Electrochemical method for preventing corrosion



ct. 25 i927.

R. VAN A; MILLS ELECTRGCHEMICAL METHOD FOR PREVENTING CORROSIN Original Filed July 21, 1924 4 v o 3/5 0//0/24/2 f /2 if/4H W# Patented Get. 25, 1927.

rf/ff ,RONALD VAN AUKEN MILLS,

NYCE, OF WASHINGTON,

oFsANDY SPRING, MARYLAND, AssiGNon 'ro- PETER Q.

DISTRICT 0F COLUMBIA.

ELECTROCHEMICAL METHOD FOR. PREVENTING CORROSION.

Application led July 21, 1924, Serial No.

The invention relates broadly to an electro-chemical method ot' preventing lcorrosion, and more particularly for preventing corrosion of well casing, tubing, and like apparatus, especially oil well apparatus,

which is very subject to coriosion due to thepresence of saline or otherfcorrosive liquids which come in contact with the tubing, casing or other apparatus, and set up electrolytic or galvanic action, which is especially marked at the tubing or casing joints.

It'is well known that corrosion is essentially ,an electrochemical .process dependent upon galvanic action, and that corrosion occurs on electro-positive surfaces,jthat is to say, the surfaces from which an electric current leaves a metal and passes into an electrolyte like salt water.

By providing an electio-pos'tive material that will corrode in preference to the iron or other 'metal in the equipment, corrosion of the equipment itself is prevented.

According to the present invention Iprovide zinc or other metal which is electropositive to iron in close proximity. to the tubing, casing or other equipment whereby the apparatus to be protected isl rendered electro-negative, and corrosion takes place from surface of the zinc or other protecting substance.

It is not necessary that the vzinc extend the full length of the tubing, but it is sufficient to provide such protectinfr material at intervals along the length of the tubing or casing.

It is further trical contact between and the zinc or other protecting material except for a limited distance. The disadvantages of the direct Contact are two-told. First, protection is localized, only the surface immediately in the vicinity of the zinc being protected, whereas whenl the zinc is spaced apart from the equipment it has been found that a much larger portion of the tubing is electrically affected, and corrosion consequently prevented. Secondly, short circuiting or contact' action takes place between the iron and zinc where the-two are desirable to avoid direct elecplaced indirect contact, which gives rise tov rapid consumption of the zinc.

According tothe present invention, I have accordingly provided special casing or tubing collars, located at the joints of successive lengths of the casing or tubing. These colthe tubing or casing 727,395. Renewed September 3, 1926.

lars are composed partly of metal, such as zinc, which is electro-posithn with respectl to the tubing or casing, the zinc being in close proximity to the inet-al surface to he protected but preferably spaced therefrom :to av id short circuiting. i

Th casing orl tubing collar serves to protect the entii'e`eqi1ipmeiit to a large extent, and 1s especially effective in preventing corrosion o t the exposed threads ot' the joint.

The inventor recognizes the well-known art of galvanizing.v metal to prevent corrosion. Galvanizing, however, possesses certain disadvantages which are eliminated by the present invention. These disadvantages are :-(1)- The thinness of the protectiiw coat of zinc. The protection lastsl only sld long as the zinc remains intact. Under the action of corrosive brines the zinc'quickly corrodes away and is dissolved and removed from the iron leaving the latter unprotected. (2) T he thin coating of zinc on galvanized iron is easily scratched or otherwise removed, thus exposing the iron. This permits the formation of a galvanic couple between the iron and zinc andstimulates the rapid consumption of the zinc.

Elie present invention eliminates these disadvantages by providing a zinc ring of sub-- stantial thickness which will withstand coi'- rosive action for a considerable period, and which is spaced away from the tubing or casing to avoid short circuiting. Furthermore, the collar which carries the protective ring may bereadil replaced at asmall cost when the vzinc has 'nally corroded away.

The invention will be more clearly understood by reference to thel accompanying drawings Fig. 1 is a view partly in longitudinal section and partly in elevation showingthe protective collar applied to a tubing or'casing joint.

Fig. A 2 is a sectional view of the same taken on line 2*-2 of Fig..1.

Fig. 3 is a view similar to Fig. 1 showing a modification. j Two lengths or separate units of well tubing or casing are shown at `10--11, each being externally threaded as at 12 and adapted to be screwed i' ternally threaded at responding threaded 1li-to receive the corportions 12 of the tubing or casin At'each jolnt there are a number of threads into a collar 13 which is inengaged in the collar and are consequently exposed to corrosive action Where the ordinary forni of collar is employed. According to the present invention corrosion of the' tub- `ing or casing andparticularly df the .exposed threads is prevented by providing zinc cast` ings 1G inside the collar and extending beyond the threaded portion of the collar. The ends 17 oi. the' outer steel or iron shell of the collar muy be beveled andturned into securely hold the zinc in place.

The zinc which is electro-positive with respect to the iron, surrounds the unengagcd threads l5 and by its electro-positive property with' respect to iron and its close proiilnity to the tubing or casing and the exposed threads thereof, protects theni against corrosion.

In Fig. 3 is shown a modified collar which may be applied to either tubing or casings. In this modification, the Zincextends for some distance beyond the steel shell as at 18 and serves to protect the body of the tubing as well as the threads of the joint. If preferred, the zinc may 'terminate at, 19

vNo. 750,807.

Having t-hus described my invention, what I claim as new and desire to secure by Letters Patent is v l. The nietho-d of protecting Well tubing against corrosion,

which consists in providing a. collar upon said tubing, said collar having a zinc ring in close proximity to the tubing but spaced therefrom.

2. The method of protecting tubing against corrosion which consists in applying collars at the joints bet-Ween of tubing, each collar being provided With an internal ring of metal which is electropositive with respect to the tubing.

In testimony whereof I allix iny'signature.

RONALD VAN AUKEN MILLS.

two, as in Fig. 1. Ob-

adjacent lengths 

